(19)
(11) EP 0 531 167 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
03.08.1994 Bulletin 1994/31

(43) Date of publication A2:
10.03.1993 Bulletin 1993/10

(21) Application number: 92308071.7

(22) Date of filing: 04.09.1992
(51) International Patent Classification (IPC)5: G03G 15/01, G03G 15/00
(84) Designated Contracting States:
DE FR GB

(30) Priority: 05.09.1991 US 755234

(71) Applicant: XEROX CORPORATION
Rochester New York 14644 (US)

(72) Inventors:
  • Scheuer, Mark A.
    Williamson, New York 14589 (US)
  • MacDonald, Daniel W.
    Farmington, New York 14502 (US)

(74) Representative: Goode, Ian Roy et al
Rank Xerox Ltd Patent Department Parkway
Marlow Buckinghamshire SL7 1YL
Marlow Buckinghamshire SL7 1YL (GB)


(56) References cited: : 
   
       


    (54) Electrostatic voltmeters readings of toner test patches for adjusting IR densitometer readings of developed test patches


    (57) In a single pass tri-level imaging apparatus (2), a pair of Electrostatic Voltmeters (ESV) (55,80) are utilized to monitor various control patch voltages (Vtb) to allow for feedback control of Infra-Red Densitometer (IRD) (54) readings.
    The ESV (80,55) readings are used to adjust the IRD readings of each toner patch. For the black toner patch, readings of an ESV positioned between two developer housing structures (58, 60) are used to monitor the patch voltage (Vtb). If the voltage (Vtb) is above target (high development field) the IRD reading is increased by an amount proportional to the voltage error. For the color toner patch, readings (Vtc) using an ESV (55) positioned upstream of the developer housing structures (58,60) and the dark decay projection to the color housing (58) are used to make a similar correction to the color toner patch IRD readings (but opposite in sign because, for color, a lower voltage results in a higher development field).






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